The present invention relates to a linear motor in which a movable member is magnetically driven between magnetic poles.
In a prior art linear motor as disclosed by JP-A-10-174418, pairs of magnetic poles adjacent to each other are magnetized by respective electromagnetic coils.
An object of the present invention is to provide a linear motor in which a number of electromagnetic coils is minimized and a magnetic flux is effectively utilized for generating an output force.
According to the present invention, in a linear motor comprising, a stator, a movable element movable with respect to the stator in a movable direction, and an electromagnetic coil device for energizing at least one of the movable element and the stator to be magnetized so that a relative movement between the movable element and the stator in the movable direction is generated by a magnetic field between the movable element and the stator, the stator includes at least one pair of magnetic core parts, and at least two pairs of magnetic poles adjacent to each other in the movable direction, the magnetic poles of each of the at least two pairs are aligned on an imaginary line perpendicular to the movable direction to generate the magnetic field passing the magnetic poles of each pair through the movable element, a magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, first one of the magnetic poles of each of the at least two pairs faces to a first side surface of the movable element, and second one of the magnetic poles of each of the at least two pairs faces to a second side surface of the movable element opposite to the first side surface in a traverse direction perpendicular to the movable direction.
Since the magnetic polar direction of one of the at least two pairs is opposite to that of another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, a size of the stator is decreased.
When one of the magnetic core parts forms both of the first one of the magnetic poles of the one of the at least two pairs and the second one of the magnetic poles of the another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, and another one of the magnetic core parts forms both of the first one of the magnetic poles of the another one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs adjacent to the another one of the at least two pairs in the movable direction, a size of the stator is minimized. When the pair of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized.
When one of the magnetic core parts forms both of the first one of the magnetic poles of the one of the at least two pairs and the first one of the magnetic poles of the another one of the at least two pairs adjacent to the one of the at least two pairs in the movable direction, and another one of the magnetic core parts forms both of the second one of the magnetic poles of the another one of the at least two pairs and the second one of the magnetic poles of the one of the at least two pairs adjacent to the another one of the at least two pairs in the movable direction, a size of the stator is minimized. When the pair of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized.
When the at least one of the movable element and the stator energized by the electromagnetic coil device has at least two parts to be magnetized respectively with a difference in energized phase between the at least two parts so that a travelling magnetic field for generating the relative movement between the movable element and the stator element in the movable direction is formed, and each of the at least two parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized.
When the stator includes at least two of the pairs of magnetic core parts and at least four of the pairs of magnetic poles juxtaposed with each other in the movable direction, each of the at least two pairs of magnetic core parts forms at least partially two of the at least four pairs of magnetic poles adjacent to each other in the movable direction, and a magnetic polar direction of one of the two of the at least four pairs of magnetic poles is opposite to a magnetic polar direction of another one of the two of the at least four pairs of magnetic poles, a size of the stator is minimized. When each of the at least two pairs of magnetic core parts is magnetized by single electromagnetic coil, a number of electromagnetic coils in the linear motor is minimized.
The movable member may include at least one of an electromagnetic coil and a permanent magnet to form pairs of magnetic poles juxtaposed with each other in the movable direction. The movable member may include pairs of high-reluctance portions and low-reluctance portions adjacent to each other in the movable direction, and the pairs of high-reluctance portions and low-reluctance portions are juxtaposed with each other in the movable direction. The movable member may be stationary while the stator is moved. The stator may be stationary while the movable member is moved. The electromagnetic coil device may energize the movable element. The electromagnetic coil device may energizes the stator. The stator may have a permanent magnet for forming therein at least one pair of magnetic poles.
When the linear motor is a multi-phase linear motor, a distance between a pair of magnetic poles of one of the at least two parts and a pair of magnetic poles of another one of the at least two parts adjacent to each other in the movable direction=(k*P)+(P/M), when P is a pitch of the pairs of the magnetic poles adjacent to each other in the movable direction in each of the at least two parts, k is an integral number not less than zero, and M is a number of the at least two parts energized with respective energized phases different from each other while M is an integral number not less than two. When the linear motor is a single-phase linear motor for moving or vibrating the movable member by a moving or vibrating width substantially equal to the pitch P of the pairs of the magnetic poles adjacent to each other in the movable direction, the magnetic polar direction of each of the at least two pairs of magnetic poles alternates while the magnetic polar direction of one of the at least two pairs of magnetic poles is opposite to that of another one of the at least two pairs of magnetic poles adjacent to the one of the at least two pairs of magnetic poles in the movable direction.
The stator or magnetic core may have an opening through which the movable member is inserted between the magnetic poles of each of the pairs in a direction perpendicular to the movable direction. A magnetic force is generated in a direction perpendicular to the movable direction and not parallel to the polar directions between the stator and the movable member, when a magnetic flux axis of the magnetic poles of at least one pair on the stator is distant away from a magnetic flux axis of the magnetic poles of at least one pair on the movable member in the direction between the magnetic poles of at least one pair on the stator. When the electromagnetic coil device has an electromagnetic coil whose circumferential part is completely surrounded by the pair of magnetic core parts as seen in the movable direction, that is, the pair of magnetic core parts extends around or over the whole outer periphery of the circumferential part of the electromagnetic coil, the electromagnetic coil is securely held or protected by the pair of magnetic core parts.